I have only found one brand, and it is not Kawasaki, does not have the rubber mated to it, and I think that is what causes the extra noise. I am like you , wish Kawasaki would make one. I have a 17 on my 2009 model, and I don't notice the extra noise, and honestly, have questioned the benefit. these are high RPM engines anyway, and love to run in the 7K range. Reducing the RPM's by about 400-500 really does not change much, just makes us feel better more than anything else.
When I was young it was wine, women, and song. Now I just get drunk and sing about women!